The vertebrate (including human) immune system recognizes microbial DNA due to the presence of specific DNA sequences containing CG dinucleotides segments without methyl groups attached. These segments are referred to as CpG motifs and can act as pathogen-associated molecular patterns (molecules recognized by the immune system). The short sequences containing CpGs are called CpG oligodeoxynucleotides (GpG ODNs). CpG motifs that are abundant in microbes such as bacteria, but rare in vertebrate DNA, induce immune responses and are considered to be immunostimulants. The primary peripheral blood mononuclear cell that is the target for CpG ODN is the plasmocytic dendritic cell.

Systemic lupus erythematosus (SLE) is an autoimmune disease where a person’s own immune system attacks the body’s healthy tissues, leading to damage in different organs. Although the exact cause of SLE is not known, this disorder features hyperactive T cells and B cells. Specific laboratory tests that directly diagnose SLE are lacking. Diagnosis is commonly achieved by identifying the presence of a variety of signs and symptoms that can occur with the disease, but not specific for it.

Innate immunity is the body’s nonspecific defense against foreign agents and is a first line of defense for the respiratory tract. For example, macrophages and neutrophils are the primary cells in the lungs that provide innate immunity. Dendritic cells are also crucial in this defense mechanism due to their ability to take up and process bacteria so that specific immune responses can take place.